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Free keywords:
Cestoda; heritability; larval life history; maternal effect; mixed mating; quantitative genetics; transgenerational plasticity
Abstract:
Parents can influence the phenotype of their offspring through various
mechanisms, besides the direct effect of heredity. Such parental effects are
little explored in parasitic organisms, perhaps because in many parasites, per
capita investment into offspring is low. I investigated whether parental identity,
beyond direct genetic effects, could explain variation in the performance
of the tapeworm Schistocephalus solidus in its first intermediate host, a
copepod. I first determined that two breeding worms could be separated
from one another after ~48 h of in vitro incubation and that the isolated
worms continued producing outcrossed eggs, that is, rates self-fertilization
did not increase after separation. Thus, from a breeding pair, two sets of
genetically comparable eggs can be collected that have unambiguous parental
identities. In an infection experiment, I found that the development of
larval worms tended to vary between the two parental worms within breeding
pairs, but infection success and growth rate in copepods did not.
Accounting for this parental effect decreased the estimated heritability for
development by nearly half. These results suggest that larval performance is
not simply a function of a worm’s genotype; who mothered or fathered an
offspring can also affect offspring fitness, contradicting the perhaps na€ıve
idea that parasites simply produce large quantities of uniformly low-quality
offspring.
